Campylobacter are Gram negative, microaerophilic, curved or spiral rods in the family Campylobacteriaceae. Campylobacter jejuni (formerly known as C. fetus subsp. jejuni) and C. coli are associated with enteritis in domestic animals and humans. Some strains of C. jejuni, C. fetus subsp. venerealis, and C. fetus subsp. fetus (also known as C fetus subsp. intestinalis and Vibrio fetus var intestinalis) cause infertility and abortions in sheep and cattle. C. fetus subsp. fetus is occasionally isolated from humans with septicemia.

Other species of Campylobacter including C. lari, C. hyointestinalis and C. upsaliensis can cause disease but seem to be of minor importance in domestic animals. Uncharacterized Campylobacter species may be involved in proliferative ileitis of hamsters, porcine proliferative enteritis and proliferative colitis of ferrets.

Geographic Distribution

C. jejuni, C. coli and C. fetus infections are found worldwide.

Transmission

Campylobacter jejuni and C coli are transmitted by the fecal-oral route; they can be spread by direct contact and on fomites including food or water. C. jejuni may also be present in the vaginal discharges, aborted fetuses and fetal membranes of aborting sheep. Undercooked poultry and other meats are sources of infection for pets and commercially raised mink. Houseflies are mechanical vectors. Humans can be infected after ingesting undercooked poultry and other meats, raw milk, raw clams, contaminated foodstuffs or unchlorinated water, and after contact with infected pets or livestock. Asymptomatic carriers are seen in many species of domestic animals; humans do not usually become carriers.

Campylobacter fetus subsp.fetus is transmitted by ingestion in cattle, sheep and goats. Animals can become infected after contact with feces, vaginal discharges, aborted fetuses and fetal membranes. This organism and C. fetus subsp. venerealis are also transmitted venereally in cattle. Genital C. fetus infections can be spread on fomites including contaminated semen, contaminated instruments and bedding. Bulls may transmit C. fetus for several hours after being bred to an infected cow; some bulls can become permanent carriers. Cows can also become carriers for years.

Campylobacter species do not tolerate drying or heating but can often survive for a time in moist environments: C. jejuni may remain viable for up to 9 days in feces, 3 days in milk and 2 to 5 days in water. C. jejuni and C. coli can remain infective in moist poultry litter for prolonged periods. C fetus can survive in liquid manure for 24 hours and soil for up to 20 days.

Disinfection

Campylobacter species are susceptible to many disinfectants, including 1% sodium hypochlorite, 70% ethanol, 2% glutaraldehyde, iodine-based disinfectants, phenolic disinfectants and formaldehyde. Common disinfectants used to treat drinking water can also kill C. jejuni. C. jejuni and fetus are inactivated by moist heat (121°C for at least 15 min) or dry heat (160-170°C for at least 1 hour). Campylobacter is also sensitive to gamma irradiation and UV radiation.

Infections in Humans

Incubation Period

In humans, the incubation period for C. jejuni gastroenteritis is 1 to 10 days and most often 2 to 5 days. The incubation period for human C. fetus infections is usually 3 to 5 days.

Clinical Signs

C. jejuni and occasionally C. coli cause enteritis; disease varies from mild gastrointestinal distress that resolves within 24 hours to a fulminating or relapsing colitis. The clinical signs may include watery or sticky diarrhea, fever, nausea, vomiting, abdominal pain, headache and muscle pain. The feces may contain blood. Complications are not common; however, reactive arthritis, hemolytic uremic syndrome and septicemia are occasionally seen. Rare complications include meningitis, recurrent colitis, acute cholecystitis and Guillain-Barré syndrome (an acute, rapidly progressive polyneuropathy). Cases of C. jejuni abortion have been seen in humans, but are extremely rare.

C. fetus is an opportunistic human pathogen and mainly causes systemic infections. Infections tend to occur in people with debilitating illnesses such as diabetes, cancer or cirrhosis. Intestinal symptoms may be mild. Fever is the only consistent symptom, but abdominal pain, splenomegaly and hepatomegaly are common. Subacute endocarditis, septic arthritis, meningitis or fever of unknown origin are also seen. Complications may include endocarditis, pericarditis, pneumonia, thrombophlebitis, peritonitis or meningoencephalitis.

Communicability

Yes. C. jejuni is found in the feces and can be shed for as long as 2 to 7 weeks in untreated infections; however, humans rarely become chronic carriers. C. fetus subsp. fetus is communicable for several days to several weeks.

Diagnostic Tests

Feces or (rarely) blood cultures are used for diagnosis. A presumptive diagnosis can be made by detecting the characteristic darting motility of the organism with dark-field or phase-contrast microscopy. Gram negative, curved or spiral rods are seen in Gram stained preparations. Definitive diagnosis is by isolation of the causative organism; however, Campylobacter is fragile and cannot always be found. Selective media or filtration techniques improve the chance of isolation. Forty-eight to 72 hour colonies are raised, round, translucent and sometimes mucoid. Biochemical testing, antigen testing and restriction endonuclease DNA analyses are used for species and strain identification.

Polymerase chain reaction (PCR)-based techniques for rapid detection or culture confirmation are also available. Serology is currently used only in research.

Treatment and Vaccination

Treatment is often limited to fluid and electrolyte replacement therapy. Antibiotics are occasionally given, particularly when the symptoms are severe or prolonged; however, their efficacy is not proven for mild infections. Individuals with Guillain-Barré syndrome usually require intensive care. Antibiotics can reduce the shedding of infectious organisms. Vaccines are not available.

Morbidity and Mortality

C. jejuni is the most common cause of bacterial diarrhea in the United States; roughly 20 cases per 100,000 population are seen yearly. Infections are particularly common in young children, and in young adults from age 18 to 29. Asymptomatic human carriers are very rare in the United States or Europe.

C. jejuni or C. coli diarrhea is usually self-limiting and generally resolves after 7-10 days; relapses can occur in approximately 10-25% of cases. Immunosuppressed individuals are at a high risk for severe or recurrent infections or for septicemia. Deaths are rare in C. jejuni infections and are seen mainly in patients with cancer or other debilitating diseases. The estimated case/fatality ratio for C. jejuni infections is one in 1,000.

Guillain-Barré syndrome is seen after approximately 1 in 1000 diagnosed infections; up to 5% of these patients may die and 30% or more may have residual weakness or other neurologic defects.

Infections in Animals

Species Affected

C. jejuni and C. coli can infect cattle, sheep, chickens, turkeys, dogs, cats, mink, ferrets, pigs, non-human primates and other species. C. fetus subsp. fetus is found in cattle, sheep and goats. C. fetus subsp. venerealis is found in cattle. Animals can be infected asymptomatically with any of these organisms.

Incubation Period

The incubation period for Campylobacter infections is generally short. Symptoms of enteritis appear within 3 days in gnotobiotic puppies and rapidly in chicks and poults.

Clinical Signs

Campylobacter species cause enteritis, abortions and infertility in various species.

EnteritisC. jejuni and occasionally C. coli cause enteritis in dogs, cats, calves, sheep, mink, ferrets, poultry and some species of laboratory animals. The clinical signs may be more severe in young animals. In dogs, symptoms can include diarrhea, decreased appetite, vomiting and sometimes fever. The feces are usually watery or bile-streaked, with mucus and sometimes blood. Symptoms generally last 3 to 7 days, but some animals may have intermittent diarrhea for weeks and occasionally for months. Calves typically have a thick, mucoid diarrhea with occasional flecks of blood, either with or without a fever. Mucoid, watery and sometimes bloody diarrhea is also seen in cats, primates, mink and ferrets. Newly hatched chicks and poults develop acute enteritis, with rapid onset of diarrhea and death.

Reproductive symptoms
In cattle, C. fetus subsp. venerealis and C. fetus subsp. fetus can cause bovine genital campylobacteriosis; this disease is characterized by infertility, early embryonic death and a prolonged calving season. Abortions are uncommon but are occasionally seen. Infected cows may develop a mucopurulent endometritis but do not usually have other systemic signs. Bulls are asymptomatic.

C. fetus subsp. fetus and C. jejuni can cause late term abortions, stillbirths and weak lambs in sheep. Infections in sheep are sometimes followed by metritis and occasionally deaths. Recovery, with immunity to reinfection, is typical. Sheep can become persistently infected and continue to shed bacteria in the feces.

Other Campylobacter infections
Other species of Campylobacter including C. lari, C. hyointestinalis and C. upsaliensis can cause disease but seem to be of minor importance. Uncharacterized Campylobacter species may be involved in proliferative ileitis of hamsters, porcine proliferative enteritis, and proliferative colitis of ferrets.

Communicability

Yes. Campylobacter species are readily transmitted between animals or from animals to humans. Organisms are present in feces, vaginal discharges and the products of abortions and can be spread by direct contact, on fomites and by arthropods acting as mechanical vectors. Contaminated food and water is often the source of infections.

Diagnostic Tests

Enteritis can be diagnosed by isolating the causative organism in fresh fecal samples; however, Campylobacter is fragile and cannot always be found. Forty-eight to 72 hour colonies are raised, round, translucent and sometimes mucoid. Biochemical testing, antigen testing and restriction endonuclease DNA analyses are used for species and strain identification. A presumptive diagnosis can also be made by observing the characteristic darting motility in darkfield or phase contrast preparations. Gram negative, curved or spiral rods are seen in Gram stained preparations. Serology on paired titers may be helpful in some cases.

Darkfield and phase contrast preparations of samples from the placenta, fetal abomasum and uterine discharge are used to diagnose Campylobacter abortions in sheep. Campylobacter antigens can also be detected by immunofluorescence.

Bovine genital campylobacteriosis can be diagnosed by detecting specific IgA in the cervical mucus; these antibodies are present for several months in half of all infected cows. Tests include a vaginal mucus agglutination test (VMAT) and enzyme-linked immunosorbent assays (ELISAs). Individual responses in the VMAT are variable; for this test, a minimum of 10 cows or 10% of the herd should be sampled. Sheath washings taken twice from bulls, approximately one week apart, can be submitted for culture or immunofluorescent testing. Vaginal cultures can also be collected immediately after abortion or infection, but this method may be unreliable: Campylobacter fetus is fragile and usually present in low numbers. Systemic antibody responses are not useful in genital campylobacteriosis, as they can be directed against nonpathogenic species.

Treatment and Vaccination

Antibiotics may be useful for some cases of enteritis; however, information on efficacy is limited. Antibiotics may also prevent exposed sheep from aborting during an outbreak. Bulls with bovine genital campylobacteriosis are sometimes treated; cows usually are not, due to practical considerations.

Vaccines are not available for enteritis, but can prevent abortions in sheep. They are also useful for both prophylaxis and treatment in bovine genital campylobacteriosis; however, vaccinated cows may remain carriers. Artificial insemination can control or prevent bovine genital campylobacteriosis.

Morbidity and Mortality

Gastrointestinal campylobacteriosis is usually self-limiting in mammals; however, up to 32% mortality may be seen with highly pathogenic isolates in chicks. Mortality is also low in adult sheep and cattle affected by abortions and infertility. Morbidity may be up to 90% in outbreaks in sheep but is usually around 5 to 50%.

Post-Mortem Lesions

In dogs, the colon may be congested and edematous. In calves, the lesions may include mild to severe hemorrhagic colitis and edematous mesenteric lymph nodes. In chicks, distention of the jejunum, disseminated hemorrhagic enteritis and focal hepatitis may be seen.

Aborted cattle fetuses may have bronchopneumonia, mild fibrinous pleuritis or peritonitis. Placentitis is usually mild; the cotyledons may be hemorrhagic and the intercotyledonary area edematous. In sheep, the fetus is usually autolyzed after C. fetus abortions; 1 to 2 cm orange/ yellow necrotic foci can sometimes be found in the liver. Placentitis may be evident, with hemorrhagic necrotic cotyledons and edematous or leathery areas between the cotyledons.